Engine starter



Oct. 19, 1943. J. E. BUXTON 2,332,055

. ENGINE STARTER I Filed March 4, 1942 subject to unnecessary wear.

Patented Oct. 19, 1943 ENGINE STARTER James E. Buxton, Elmira, N. Y., assignor to Bendix Aviation Corporation, corporation of Delaware South Bend, Incl, a u

Application March 4, 1942, Serial No. 433,311

4 Claims.

The present invention relates to engine starters and more particularly to a drive of the type in which a pinion is maintained in engagement with an engine gear as long as the starting motor rotates above a predetermined speed, the pinion being permitted to overrun by virtue of an overrunning clutch connection.

In starter drives of the above type such as disclosed in the patent to Kearney, No. 2,218,972, it sometimes happens that the operator keeps the starting switch closed while holding the engine throttle open to overcome a vapor lock condition or for other reasons. Under these conditions the pinion is held in mesh with the engine gear and overruns the starting motor; and if the practice is persisted in, the overrunning clutch is In aggravated cases the overrunning clutch may even seize and cause the starting motor to rotate at a dangerously high speed.

It is an object of the present invention to provide a novel engine starter drive in which the gearing is normally held in mesh as long as the starting motor rotates above a predetermined low speed.

It is another object to provide such a device in which the gearing is arranged to be disengaged responsive to a predetermined high speed of rotation of the starting motor.

It is another object to provide such a device in which the high speed limit is substantially above the speed attained by the pinion when the engine is started in a normal manner.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation partly broken away and in section showing a preferred embodiment of the invention with the parts in idle position;

Fig. 2 is a section taken substantially on the line 2-2 of Fig. 1;

Fig. 3 is a view similar to Fig. 2 showing the parts in the positions assumed while the pinion is being held in mesh with the engine gear by its centrifugal latch, and

Fig. 4. is a View similar to Fig. 2 showing the parts in the positions assumed when the centrifugal latch is released by the high speed centrifugal controlling member.

In Fig. 1 of the drawing there is illustrated a power shaft I which may be the extended armature shaft of the starting motor not illustrated. Shaft I is provided with a smooth reduced extension 2 forming a shoulder 3, and a screw shaft 4 is fixed on the outer end of said extension as by means of a cross pin 5 retained by a lock wire 6. A pinion l is slidably journalled on the smooth portion 2 of the power shaft, being normally located adjacent the end of the screw shaft 4 and slidable longitudinally into engagement with an engine gear 8, the operative position of the pinion being defined by the shoulder 3. i

Means for traversing and rotating the pinion from the screw shaft 4 is provided comprising a nut member 9 threaded on the screw shaft, and a barrel member H encircling the nut and having a clutch member l2 fixed in its forward end in any suitable manner as indicated at l 3. An overrunning clutch connection is provided between the clutch member i2 and the pinion comprising a flange member M fixed to the pinion having clutch teeth adapted to mesh with corresponding clutch teeth on the member 12.

The nut member 9 is provided with a radial flange I5 having a loose fit within the barrel II, and is retained in the rear end of the barrel by means such as a split lock rin [6. A cylindrical.

block I! of elastically deformable material such as rubber is seated on the nut in abutting relation with the flange l5 and normally loosely bearing against the adjacent surface of the clutch member l2. A sleeve I8 i preferablyprovided within the elastic member l1, having a bearing fit. on the nut 9 and having a radial flange I 9 abutting the clutch member I 2. A springzlis mounted on the extended hub 22 of pinion 'Lbeing retained thereon by a thimble 23 and lock ring 24, and arranged to bear on the clutch member l2 to normally maintain the teeth of the clutch members in engagement. V

Means are provided for maintaining the pinion l in mesh with the engine gear 8 until thelengine has become reliably self-operative.

25 mounted in the nut member 9 with freedom for radial movement, and adapted'to engage a notch 26 in the screw shaft so as to prevent backward rotation-of the nut on the screw shaft.

Means responsive to rotation of the nut above a.

As hereshown this means is in the form of alatch pin shaft and to enter th notch 25 when it comes into registry therewith.

According to the present invention means are provided for releasing the centrifugal latch in response to rotation of the control nut 9 above a predetermined high speed. As illustrated, this means is in the form of a second centrifugal lever 33 pivoted at 34 to the control nut, having a weighted arm 35 adapted to move out under centrifugal force, and a short arm 36 arranged to bear on the free end of the lever 21 and move it inwardly. A comparatively heavy spring 38 is arranged to oppose the action of the centrifugal level 33, the strength of this spring and the weight of the arm 35 being so proportioned that the lever 33 is caused to perform its releasing function at the desired predetermined high speed.

In the operation of this device, starting with the parts in positions illustrated in Fig. 1, rotation of the power shaft I causes the pinion to be moved longitudinally into mesh with the engine gear 8 until the pinion engages the shoulder 3 on the power shaft. Further rotation of the power shaft causes the nut 9 to compress the elastic member I! within the barrel II between the flange l5 of the nut and the adjacent surface of the clutch member l2, thus pressing the clutch member l2 against the toothed flange M of the pinion and establishing a yielding driving conmotion between the nut and pinion. When the engine starts, the acceleration of the pinion I by the engine gear is transmitted back to the nut 9 causing it to overrun the screw shaft and move backward, thus releasing the pressure on the elastic member I1. At this time, however, the nut 9 is rotating at sufficient speeed to cause the centrifugal lever 21 to press the latch pin 25 against the screw shaft so that it enters the notch 26 and prevents further retrograde movement of the nut. Since the clutch member I2 is now held against the pinion flange l4 only by the light pressure of the spring 2 l the pinion is permitted to overrun freely, this overrunning action being preferably facilitated by forming the teeth as ratchet or saw-tooth dentils as illustrated.

Under normal conditions, this situation will continue as long as the operator keeps the starting switch closed and the starting motor energized. When the starting switch is opened and the drive shaft l and nut 9 decelerate below the predetermined minimum speed, the spring 3| withdraws the latch pin 25 from the notch 26 of the screw shaft and the nut is then permitted to return to idle position, thus withdrawing the pinion 1 from engagement with the engine gear.

If during the overrunning condition of the drive, the operator should open the accelerator of the engine so as to cause the engine to race, sufficient torque may sometimes be transmitted through the binding of the pinion 'I on the drive shaft to cause the drive shaft to rotate at a dangerous speed. Under such circumstances, as soon as the rotation of the nut 9 exceeds the predetermined high speed limit, the weighted arm of lever 33 moves out against the action of the spring 38 and retracts the lever 21, thus permitting the latch pin 25 to be withdrawn, whereupon de-meshing of the pinion takes place in the usual manner. The strength of the spring 38 is preferably so chosen that the releasing action of lever 33 takes place at or about the maximum free spinning speed of the starting motor.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the parts without departing. from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In an engine starter drive a power shaft, a member having a threaded connection therewith,

a pinion having an overrunning connection with the member and movable thereby into and out of engagement with a member of an engine to be started, releasable means for resisting movement of the member to disengage the pinion from the engine gear means responsive to centrifugal force for actuating the resisting means, and means for overcoming the centrifugal means and releasing the resisting means responsive to a predetermined high speed of rotation of the member.

2. In an engine starter drive a power shaft, a member having a threaded connection therewith, a pinion having an overrunning connection with the member and movable thereby into and out of engagement with a member of a engine to be started, means holding the pinion in mesh with the engine gear centrifugal means for actuating the holding means, means for overcoming the actuating means and releasing the holding means at a predetermined low speed of rotation of the member, and means for overcoming the actuating means and thereby permitting releasing of the holding means responsive to a predetermined high speed of rotation of the member.

3. In an engine starter drive a pinion adapted to engage and drive a gear of an engine to be started, means for actuating the pinion including a member having an overrunning clutch connection therewith, releasable means for holding the pinion in mesh with the engine gear, centrifugal means for moving the holding means into operative position, spring means for releasing the holding means at a predetermined low speed of rotation of the member, and means for overcoming the centrifugal means and thereby permitting release of the holding means responsive to a predetermined high speed of rotation of the member.

4. In an engine starter a screw shaft, a nut threaded thereon, a pinion having an overrunning clutch connection with the nut and movable thereby into engagement with an engine gear, means including a latch rotatable with said member and movable to engage the screw shaft and resist movement of the pinion out of engagement with the engine gear, centrifugal means for actuating the latch,. spring means for overcoming the centrifugal means and releasing the latch at a predetermined low speed of rotation of the member, and means for overcoming the centrifugal means and permitting the release of the latch at a predetermined high speed of rotation of the member.

JAMES E. BUXTON. 

